Numerous compositions and processes for cleaning plastic surfaces in an industrial setting are currently known in the art. Most of them contain acid, surfactant(s), and phosphates. Alkaline cleaners are also known to provide good removal of oily soils, but are considered undesirable for certain uses, such as by way of non-limiting example cleaning polymeric materials. Alkaline cleaners have drawbacks including difficulty in controlling etch rate and bath parameters, as well as residue left behind on the cleaned surface. Also, in some locations, phosphates are forbidden or severely limited to avoid potential pollution and eutrophication of bodies of water that receive discharges of industrial waste water. Thus, acidic cleaning compositions that contain little or no phosphorus-containing components, but are still effective cleaners have been sought.
Acidic cleaners are known for use in removing industrial contaminants, such as forming lubricants, fingerprints and other soils prior to further treatment steps or coating. Conventional acidic cleaners require working bath temperatures of at least 130° F. for effective cleaning. While the high temperatures facilitate cleaning and have the added benefit of reducing microbial growth in the bath, the high temperature requirements have drawbacks. The need to maintain large volumes of cleaner at temperatures well in excess of ambient temperatures requires heating equipment and energy, which increases the cost of manufacture. High temperature baths also exhibit higher volume loss rates due to evaporation. Finally, more safety precautions must be taken when working with high temperature baths. For these and other reasons, it is desirable to provide an acidic cleaner that provides cleaning, which is at least as good as high temperature acidic cleaners, at measurably lower bath temperatures.
The benefits of running a cleaner bath at low temperature must be balanced against the resulting increase in microbial growth in the cleaner bath. One consideration in any cleaner that comprises organic material, such as surfactants and soils, is the possibility that the cleaner will support microbial growth, e.g. fungal and/or bacterial. Microbial growth can reduce the efficacy of the cleaner, generate sludge and pose a health hazard depending on the species of microbes present. It is desirable to provide a cleaner that reduces microbial growth both in the concentrate and in the working cleaner bath at low temperature.
A ubiquitous component of alkaline and acidic cleaners is surfactant. A drawback of many surfactants found in conventional products is the foamy nature of the cleaner. Particularly where oily soils are to be removed, the surfactants that work well for dissolving or dispersing oily soils into aqueous solutions generally tend to be foamy. A variety of common household products provide alkaline or acidic cleaner with surfactant, but are quite foamy. While foaming is considered desirable in many consumer products, foaming is undesirable in industrial applications, particularly where pressurized spray cleaners are used. A traditional household cleaner used in such an application rapidly generates unmanageable amounts of foam. It is desirable to provide a low foam cleaner suitable for use in industrial spray cleaning.